1. Field of the Invention
This invention relates to a method of manufacturing composites wherein the bonding medium is a thermoplastic or thermocuring resin.
2. Description of Related Art
The term "composite" is a word in common usage in industry to identify a component or product produced by impregnating a fibrous material with a curing resin to form laminates or layers.
Such composites are well known and widely used in industry, particularly for the production of high strength, lightweight components such as components for the marine and aircraft industries. One of the requirements in manufacturing such composites is to expel all air and excess resin from within the composite so as to provide a complete bond between the respective components of the composite to achieve maximum strength and to minimise weight. Further to reduce manufacturing times and improve the products performance, it is customary to cure the component at an elevated temperature.
In currently employed manufacturing methods, it is common to use vacuum bags as a means of applying pressure to the composite to force air out of the interior thereof and remove excess resin. Also curing of the composite in an autoclave or the like effects additional compaction, and provides the ability to control the temperature to ensure complete curing and, in some situations, to accelerate curing. An alternative known technique is to use a conventional press, preferably with heated dies, to compress the elements of the composite and to accelerate curing.
Both an autoclave and a heated moulding presses each require substantial mechanical equipment to effect the curing operation, which can be a major cost and convenience factor, particularly in producing large size composites. Also metal moulds and autoclaves are very expensive in terms of capital cost, and particularly in the case of an autoclave is expensive to operate.
Resin transfer moulding is another known process for the production of composites but it does demand a high degree of accuracy and skill in the mould construction and in the implementation of the moulding process. Problems are experienced in obtaining accuracy in placement and distribution of the fibre and the resin within the mould. In attempting to deal with these problems it is commonly necessary to use special high flow resins and high quality fibre materials. These add to the product cost as also does the slow process times required for longer products.